NUCOR has pioneered a giant mini-mill in which steel is poured into continuous casting machines and, from there, straight onto a hot strip mill without having to make slabs first.
NKK's Keihin steel complex developed another system replacing separate coking ovens and sinterers with a blast furnace with two smaller furnaces attached above.
Iron ore powder poured into the top of the structure passes through the two small furnaces where it is sintered using gases generated when ordinary coal, rather than coke, is put into the main chamber and burned, producing pig iron.
The new process is estimated to cut production costs by 10%.
The most common technology in mini-mills, thin slab casting, was developed by SMS and put into use by NUCOR.
Electric arc furnaces burn scrap metal, rather than ore, into molten steel which is formed into slabs just two inches thick which are immediately compressed into even thinner finished steel.
The process is much quicker and less capital intensive than traditional steel-making, but depends on an inexpensive supply of scrap metal and electricity and the steel produced is not of the highest quality.
Co-Steel, in addition to NUCOR, built mini-mills employing thin slab casting.
Companies considering or planning such plants are: Madrid; U.S. Steel; ARRCO; Eko Stahl; a consortium of Broken Hill Proprietary and North Star Steel; a consortium of TRICO Steel, British Steel and Sumitomo Metal Industries; and ISCOR and the South African Industrial Development Corporation.
